Phosphopyruvate Dehydratase



Pathway and reaction catalyzed with metabolite structures
In preparation for the final step of glycolysis, Enolase is used as a catalyst to turn 2-phosphoglycerate (2-PGA) into phosphoenolpyruvate (PEP). It dehydrates the alcohol by removing a water molecule and simultaneously making a double bond between the two carbons not directly connected to the hydroxyl group. This step makes the compound relatively unstable, but also gives energy in order for the final step to occur. Enolase is also that catalyst in the reverse reaction to make PEP into 2-PGA again. As with the reaction below, Enolase must have a divalent metal cation present to activate or deactivate the enzyme. The best cofactor would be Mg2+, but many, including Zn2+, Mn2+ and Co2+ can be used. The metal ion works by binding to the enzyme at the active site and producing a conformational change. This makes it possible for the substrate (2-PGA) to bind at the Enolase active site. Once this happens, a second metal ion comes in and binds to the enzyme to activate the Enolase catalytic ability.

Other interesting information
Enolase is present in all tissues and organisms with the ability to do glycolysis or fermentation. Recent studies have Enolase concentration samples in order to determine certain conditions and their severity. For instance, high concentrations of Enolase in cerebrospinal fluid (CSF) are more strongly associated with astrocytoma than other enzymes like aldolase, pyruvate kinase, and creatine kinase. High concentrations of Enolase in the CSF are also linked to the fastest rate of tumor growth and increased chances of heart attack or stroke. Enolase can be competitively inhibited by fluoride for the substrate 2-PGA. In drinking water with added fluorination, oral bacteria Enolase activity is inhibited without harmed humans. This works to prevent cavities.

Enolase Scenes
Overview

Secondary Structure

=Fumarase or Fumarate Hydratase=

Pathway and reaction catalyzed with metabolite structures
Fumarase is used in the citric acid cycle to conduct a transition step in the production of energy to make NADH. It metabolizes Fumarate in the cytosol, which becomes a byproduct of the urea cycle and amino acid catabolism. It catalyzes the addition of water to make S-Malate. This is a reversible reaction.

Other interesting information
Fumarase is dominant in fetal and adult tissues and largely expressed in the skin, parathyroid, lymph, and colon There are two classes of Fumarases, which depend on the arrangement of their relative subunit, their metal requirement, and their thermal stability. Class I Fumarases can change their state or become inactive when exposed to heat or radiation. They are sensitive to superoxide anions and Fe2+ dependent. Class II Fumarases are found in eukaryotes and prokaryotes. They are iron-independent and thermal-stable. Fumarase deficiency is an autosomal recessive metabolic disorder distinguished by a deficiency of the enzyme Fumarate hydratase and indicated by an excess of Fumaric acid in the urine. It is common of infants with neurologic abnormalities and its potential causes include cytosolic and mitochondrial forms of Fumarase.

Fumarase Scenes
Overview

Secondary Structure

Hydrophilic

Author
Originally Completed by Sydney Park